Often, yes, after unfreezing.

That is great! I was affraid of the specimens could be damaged from freezing process. Do you know if should I have a specific care or procedure during unfreezing?

Only tangential to your question, but may be of interest for zoo nutrition. Ginger root and chicory root are often added to livestock diet as antihelminthic agents. Wild chicory is often considered a weed, and may be harvested often as a community service. Chicory root also contains the prebiotic inulin, which may improve bowel function and general health.

There can at least sometimes be damage of a nature that does not necessarily present a "total" problem as far as identification of helminths is concerned. This damage might or might not be related to autolysis or decomposition or whatever, i.e. perhaps not to freezing. Probably depends partly on how long the intestine was lying around for before freezing. I don't know of anything specific that needs to be done when unfreezing. Not related to helminths, but when meat containing Sarcocystis has been frozen, it is still possible, after unfreezing, to determine the ultrastructure of the tissue cyst wall (i.e. the fine structure; by electron microscopy). This is a feature that is often taken into account for species identification of Sarcocystis.

Thank you so much! This is really good, I have important samples in this condition to work with and would be terrible to waste them. Can you indicate any paper saying this? 

I am the author of the Sarcocystis story (it is published), but presumably it is the helminths that you are referring to. See the two papers listed below. I might have one or both of them (and possibly other reports involving frozen helminths) in my office. Am about to go to a conference, however, so will next be in the office after 5 August, by which time you might have gotten somewhere with this matter (if not, let me know). "Freshly" collected helminths, particularly certain kinds, should often NOT be placed directly into fixative, as you might be aware. They need to be relaxed first (leaving aside the matter of how to do that). Otherwise, diagnostic features can be obscured. You need to ask an expert helminth taxonomist about exactly what to do in this respect with helminths that have been frozen. It might be safest to relax them, unless it is certain that this is not necessary (as long as that would not do any "harm", which it probably won't). REFERENCES: Mayer, K.A. et al. 2003. Helminth parasites of the southern sea otter Enhydra lutris nereis in central California: abundance, distribution and pathology. Diseases of Aquatic Organisms 53 (1): 77-88; Brattey, J. & Stenson, G.B. 1995. Helminth parasites of the alimentary tract of the Harbor Porpoise, Phocoena phocoena (L.) from Newfoundland and Labrador. Journal of the Helminthological Society of Washington 62 (2): 209-216.

I'll take a look in the references. Thank you so much for your help! And have a nice Conference! All the best

Yes, look in the "Materials and Methods" sections of those papers (for a start).

The Sarcocystis reference (although I have assumed it was helminth-associated information that you wanted) appears below. It contains electron micrograph images of the appearance of tissue cysts after freezing. I have reprints of the publication. REFERENCE: Kaiser, I.A. & Markus, M.B. 1981. Sarcocystis in the avian intermediate host. Proceedings of the Electron Microscopy Society of Southern Africa 11: 115-116.

Thanks for the conference wishes and good luck with the helminths!

P.S.: If you are not already aware of these things, and you have more of the digestive tract than only the intestine, check on whereabouts the various helminths can occur. Also, care must be taken not to break worms that are attached to the gut wall. E.g. the scolex of a tapeworm can be important for identification, as you might know. Therefore, you can't simply pull it and leave the scolex behind, attached to the mucosa.   

Absolutelly! Broken worms can not be identified. I have all intestinal tract to look at, and even lungs, kidneys, liver.... Thank you so much!

There is a way to preserve helminth structure in paleoparasitology working with coprolites. That is rehydrating the samples during 72 hours with 0.5 percent Trisodium Phosfate (TSP). This solution preserves helminthic structures.  There are many papers where this method is mentioned. For example one is the following: First paleoparasitological analysis in archaeological samples of Northwest Pampa Region by authors Fabra, Ramirez and Ferrero. You can also consult in your country an expert in paleoparasitology Dr. Adauto Araujo.  Most probably he may tell you how to preserve and rehydrate helminth structures. He works in Fundación Oswaldo Cruz in Río de Janeiro. I hope this can help. Good luck!!

Nice thought. However, techniques for coprolites, for instance (which we have used: Evans AC, Markus MB, Mason RJ & Steel R, 1996, Late Stone-Age coprolite reveals evidence of prehistoric parasitism, S Afr Med J 86: 274-275) are not applicable to frozen helminths. The latter do not require specific rehydration. Merely unfreezing. The structure of unfrozen helminths is normally basically intact, so to speak, because the worms have usually not dried out.

Yes; I think so - it ist often (but not always!) possible!

Yes as long as the organisms or the helminths have not been destroyed

It will also depend on the state of the intestines when they are frozen; are they freshly prepared?

Yes Moses, they were fresh when frozen.

It is posible to identify the parasites. you can make an qualitative analysis, but not a quantitative one because some parasites are destroy, but some others remains intact. We freeze animals and then look for parasite successfully. regards. Gabriela

Thanks María Gabriela. Do you use any special protocol for unfreezing hosts and parasites?

It is better to examine the dissected organism immediately searching for helminth so the freezing is un-desirable idea

no, just un-freeze at room temperature. AS Adnan said, always is better examine the organ and parasite in fresh.

Just to add something to all comments and suggestions, if you have a long intestine, what you can do is to separate it in sections, then you defrost one piece and then another, in this way you avoid decomposition of the rest of helminths in the remaining intestinal sections, because remember, they are not fixed yet, only frozen! Good luck! 

This is a good point that Carlos has made. I was also tempted to add some words of caution concerning the post-unfreezing situation, although I did mention previously that decomposition can sometimes take place pre-freezing, depending on the circumstances prevailing around that time. If memory serves me correctly, it is stated in one of the articles which I listed in a previous posting here, that the intestine was removed while still partly frozen. This is a time at which it could potentially be cut easily. One way or another, you want to avoid leaving a whole unfrozen intestine (or whatever organ) lying about for an unnecessarily long period. To perhaps state the obvious: When not working with e.g. an unfrozen intestine, keep it at around 4 degrees C. temporarily, or perhaps on ice. Which reminds me that in the past, when I relaxed helminths prior to fixing, the relaxing process took place at 4 degrees C.

It depends on what you are looking for. For example,  you can find Strongyloides stercoralis  with a fine needle from a part of defreezed  intestine under the stero  microscope.